Expert Strain Testing for Static and Dynamic Loads

Validation of how structures carry load and what kind of stress distribution exists is important for confirming structural design and integrity. Analysis predictions provide critical guidance in the design process, while testing provides confirmation of the analysis model’s predictive capabilities and the physical hardware’s performance. Strain testing is a direct approach for obtaining the information necessary to build confidence in a structure’s ability to perform as designed.

Strain testing allows both static and dynamic loads to be evaluated and can be used to troubleshoot existing systems to identify when there may be problems. When a structure has failed, strain testing can guide the detailed evaluation to determine the loading conditions that led to the failure. Strain testing allows the true environment to be identified to assess whether fatigue or overload conditions exist. Coupled with finite element analysis, strain testing allows thorough structural assessment for design validation. ATA is expert at conducting strain testing on existing structures at remote locations in the field.

Static Strain

Proof load testing is conducted to ensure that static or pseudo-static design loads can be handled by a structure. When these proof loads are applied, strain measurements are key to validating that the stress and load distribution in the structure are as expected and there are no unexpected hot-spots. ATA is expert at installing strain gages as and using finite element models (FEMs) to identify the critical locations where strain measurements are the most effective. ATA can provide assistance in the instrumentation installation process as well as signal conditioning and strain data collection and stress level monitoring.

Dynamic Strain

Dynamic stresses occur in all structures exposed to operational conditions. Dynamic strain measurements are key to identifying those dynamic conditions and determining whether they pose a risk to the structure. Fatigue and durability must be assessed to ensure that design life criteria are met. ATA has a long history of installing strain gages to monitor structural stresses during dynamic operating conditions. Our data acquisition equipment is tailored to allow simultaneous collection of multiple instrumentation parameters that can be used to evaluate structural integrity and fatigue life. The measurements listed here couple with the strain measurements to collectively allow clearer evaluation of the dynamic environment that the structure is exposed to and determine how dynamic loading affects the structural performance.

Strain

Load/pressure/acoustics

Speed/tachometer

Acceleration

Displacement

Temperature

ATA engineers are dynamics specialists with the experience to conduct dynamic strain testing using sophisticated instrumentation to provide a clear picture of structural responses and performance.

Operating Loads

Strain gages, when properly installed, can be used as load sensors on existing structures. Load measurements are often desired on structures where it is difficult or impossible to install a load cell for the desired measurements. Arrays of strain gages can be used to provide independent load measurements when they are properly distributed.

ATA has developed methods for measuring structural operating loads based on strain readings and a series of strain-to-load calibrations. Using the test-measured strain-based loads and detailed FEMs, we can then provide our customers with accurate fatigue life predictions on components or in areas where strain readings are impossible to obtain. ATA has conducted numerous test programs on vehicles and other structures using strain gage arrays that can be combined in an independent manner to yield the desired load conditions. Independent loads are applied to the structure while strain arrays are monitored to develop the needed strain transformation matrix to be applied to the strain measurements. Once the strain measurements are made, the data is processed to yield the desired operating loads.

Data Acquisition

ATA is equipped with multiple strain conditioning and acquisition systems capable of providing quality test results in a variety of environments. Testing outdoors at our customer’s field site is a typical environment for our strain data acquisition systems. Our hardware is specifically designed for environments ranging from temperature-controlled lab conditions to extreme locations where temperature, moisture, vibration, dirt, and oil would damage or destroy other systems. Our data acquisition systems can sample at rates over 100,000 samples per second simultaneously for over one hundred channels.